As to amino acid or peptide-modified silicones and their preparation, a variety of compounds and preparation methods are under investigation. For example, amino acid derivative-modified silicones of the formula shown below are known from JP-A 2004-182680. These amino acid derivative-modified silicones have a structure in which the amino and carboxyl groups of amino acid are protected. While they are prepared using isocyanates or dicyclohexylcarbodiimide, use of such toxic compounds is undesired from the safety aspect. Because of their complex structure, the compounds cannot be prepared in a simple way.

JP-A 2009-540040 discloses that reaction of N-acylamino acid with amino-functional siloxane produces salt and amide compounds. It is described that on thermal reaction, dehydration occurs via a salt compound to form an amide. It is also described that the salt compound is easily obtained, but the dehydration/amidation reaction is slow and it is thus difficult to selectively obtain the amide compound. Namely, the amide compound is obtained while the salt compound is left therein. Due to its nature, the salt compound cannot remain stable at pH levels outside the neutral region. With respect to the amino acids of N-unprotected type having primary, secondary or tertiary amino group, allegedly no effective reaction can be carried out.
In the prior art, amino-modified organopolysiloxanes are known to exert surface protection and softening effects since they adsorb to hair due to the inclusion of amino groups in the molecule (see JP-A H01-190619). In general, hair care cosmetics are kept below pH 5 for preservation or other purposes. Blending the amide compound with some salt left therein in such compositions fails to improve combing and smoothness in hair.
JP-A 2000-143797 discloses that a peptide-silicone copolymer of the formula shown below is obtained utilizing an ability of aspartic acid to form polysuccinimide. The reaction is dangerous because of a high temperature in excess of 160° C. The yield is low since side reactions occur to form unnecessary components, posing a need for extra steps of filtration and washing.

Further, JP-A H03-223207 describes reaction of one end epoxy-modified silicone with an amino group of peptide. This method is undesired since the reactant, epoxy-modified silicone is toxic.